The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Resistive devices such as layered heaters or load resistors are typically used in applications where space is limited, when heat output needs vary across a surface, or in ultra-clean or aggressive chemical applications. A layered resistive device, such as a layered heater, generally comprises layers of different materials, namely, a dielectric and a resistive material, which are applied to a substrate. The dielectric material is applied first to the substrate and provides electrical isolation between the substrate and the resistive material and also minimizes current leakage during operation. The resistive material is applied to the dielectric material in a predetermined pattern and provides a resistive heater circuit. The layered heater also includes leads that connect the resistive heater circuit to a heater controller and may include an optional over-mold material that protects the lead-to-resistive circuit interface. Accordingly, layered load devices are highly customizable for a variety of applications.
Individual layers of the resistive devices can be formed by a variety of processes, one of which is a “thick film” layering process. The layers for thick film resistive devices are typically formed using processes such as screen printing, decal application, or film printing heads, among others. In some applications, one or more of the layers may be formed of a section of tape or other flexible sheet of material that may be handled and manipulated to conform to the geometry of the substrate. The tape generally does not exhibit adhesiveness or tackiness, and as such, a process must be utilized to adhere the tape to the substrate. The tape must be positioned on the substrate during the adhering process. Such positioning may be performed manually by a human operator, however, such manual application of the tape or preform may lack speediness and reliability in the positioning process. The use of thick film tape on a layered load device was disclosed in pending U.S. patent application Ser. Nos. 11/779,703 and 11/779,745, which are hereby incorporated by reference in their entireties.